TUESDAY, May 14 (HealthDay News) -- Hollywood film star Angelina Jolie announced Tuesday that she has undergone a double mastectomy because she carries a genetic mutation that greatly increases her risk of potentially fatal breast cancer.

She said she began the process to have both of her breasts removed in early February because she lost her mother, actress Marcheline Bertrand, to ovarian cancer when her mother was just 56.

Jolie, 37, revealed details of her surgery in an op-ed article in Tuesday's The New York Times. Writing about her mother's nearly 10-year-long battle with breast cancer, Jolie said: "She held out long enough to meet the first of her grandchildren and to hold them in her arms. But my other children will never have the chance to know her and experience how loving and gracious she was."

Jolie, who has six children with her companion and fellow film star Brad Pitt, said she often finds herself trying to explain to her children about the disease that killed her mother. "They have asked if the same could happen to me. I have always told them not to worry, but the truth is I carry a 'faulty' gene, BRCA1, which sharply increases my risk of developing breast cancer and ovarian cancer," she wrote.

The BRCA1 and related BRCA2 genes belong to a class of human genes known as tumor suppressors. According to the U.S. National Cancer Institute, in normal cells, the BRCA1 and BRCA2 genes help to maintain the stability of a cell's genetic material -- called DNA -- and help prevent uncontrolled cell growth. Mutation of these genes has been linked to the development of hereditary breast and ovarian cancer.

An estimated 12 percent of women -- or 120 out of 1,000 -- in the general population will develop breast cancer during their lives. But in women with a mutation in BRCA1 or BRCA2 genes, the risk of breast cancer increases dramatically. Approximately 60 percent of women -- 600 out of 1,000 with these genetic mutations -- will be diagnosed with breast cancer. Said another way, a woman who has inherited a harmful BRCA1 or BRCA2 mutation is about five times more likely to develop breast cancer than a woman who doesn't have such a mutation, according to the U.S. National Cancer Institute (NCI).

These genetic mutations are most commonly found in Jewish women of eastern European descent. Also, Norwegian, Dutch, and Icelandic peoples have higher rates of BRCA1 and BRCA2 mutations, according to the cancer institute.

A double mastectomy involves removing as much "at-risk" tissue as possible to reduce the risk of cancer. The procedure does not, however, guarantee complete protection against cancer, according to the NCI.

Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, called a double mastectomy "the best option for someone who is BRCA-positive."

"The risk of cancer is extremely high and we know that you can watch them, but there is no guarantee that you will catch the cancer at an early stage," she said. "If you have the ability to prevent a cancer that's probably the best route," Bernik explained.

"Not everyone wants a prophylactic mastectomy and they don't all do that," Bernik said. "But women should certainly be informed," she added.

Bernik said more women are opting for the procedure. "The reconstructive options have improved dramatically over the past 15 years. So women can at least feel confident knowing that if they remove their breasts they will be left with a very good to excellent cosmetic result," she said.

Writing in the Times, Jolie said, "My doctors estimated that I had an 87 percent risk of breast cancer and a 50 percent risk of ovarian cancer, although the risk is different in the case of each woman.

"Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much as I could. I made a decision to have a preventive double mastectomy."

Jolie said the process of having her breasts removed was finished by late April, and included the reconstruction of both breasts with implants. "There have been many advances in this [reconstruction] procedure in the last few years, and the results can be beautiful," she wrote.

According to the NCI, genetic testing can reveal whether a woman carries a BRCA1 or BRCA2 mutation. There are benefits to such testing, whether a woman receives a positive or a negative result. "The potential benefits of a negative result include a sense of relief and the possibility that special preventive checkups, tests, or surgeries may not be needed. A positive test result can bring relief from uncertainty and allow people to make informed decisions about their future, including taking steps to reduce their cancer risk," the agency said.

For her part, Jolie said: "I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made. My chances of developing breast cancer have dropped from 87 percent to under 5 percent. I can tell my children that they don't need to fear they will lose me to breast cancer.

"For any woman reading this, I hope it helps you to know you have options. I want to encourage every woman, especially if you have a family history of breast or ovarian cancer, to seek out the information and medical experts who can help you through this aspect of your life, and to make your own informed choices."